Buck Power Stage | PartQuest™ Explore

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Mike Donnelly
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Mike Donnelly

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10 years 8 months

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Member of the PartQuest Explore Development Team. Focused on modeling and simulation of analog, mixed-signal and multi-discipline systems covering a broad range of applications, including power electronics, controls and mechatronic systems.

Description

This design shows the importance of choosing the right inductor size and type, to avoid saturation-induced current spikes during operating transients. In this case, the start-up transient in two nearly identical open-loop buck power stages (12V -&gt; 3V) is examined. The only difference is that the top circuit is using an inductor calibrated to a Coilcraft XAL6060-223 (22uH), which has "soft saturation" behavior. The bottom circuit is using a similarly sized inductor, but with a more typical "hard saturation" characteristic.

Both inductors work well for the steady-state load condition of 3 Amp. But during the turn-on transient, that current can go significantly above that nominal level. At that time, the instantaneous inductance of the hard-saturating device collapses, resulting in even larger current spikes in each switching interval. Note in the waveforms on the left: The soft-saturation inductance drops to 14uH minimum during the transient, whereas the hard-saturation inductance crashes to near 2uH, or only 10% of its nominal value!

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Copy of Compare Soft Saturation vs. Regular Inductor - Switching - on Fri, 07/12/2024 - 22:25

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Description

This design shows the importance of choosing the right inductor size and type, to avoid saturation-induced current spikes during operating transients. In this case, the start-up transient in two nearly identical open-loop buck power stages (12V -&gt; 3V) is examined. The only difference is that the top circuit is using an inductor calibrated to a Coilcraft XAL6060-223 (22uH), which has "soft saturation" behavior. The bottom circuit is using a similarly sized inductor, but with a more typical "hard saturation" characteristic.

Both inductors work well for the steady-state load condition of 3 Amp. But during the turn-on transient, that current can go significantly above that nominal level. At that time, the instantaneous inductance of the hard-saturating device collapses, resulting in even larger current spikes in each switching interval. Note in the waveforms on the left: The soft-saturation inductance drops to 14uH minimum during the transient, whereas the hard-saturation inductance crashes to near 2uH, or only 10% of its nominal value!

About text formats

Copy of Compare Soft Saturation vs. Regular Inductor - Switching - on Fri, 07/12/2024 - 22:07

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4 years 6 months

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Description

This design shows the importance of choosing the right inductor size and type, to avoid saturation-induced current spikes during operating transients. In this case, the start-up transient in two nearly identical open-loop buck power stages (12V -&gt; 3V) is examined. The only difference is that the top circuit is using an inductor calibrated to a Coilcraft XAL6060-223 (22uH), which has "soft saturation" behavior. The bottom circuit is using a similarly sized inductor, but with a more typical "hard saturation" characteristic.

Both inductors work well for the steady-state load condition of 3 Amp. But during the turn-on transient, that current can go significantly above that nominal level. At that time, the instantaneous inductance of the hard-saturating device collapses, resulting in even larger current spikes in each switching interval. Note in the waveforms on the left: The soft-saturation inductance drops to 14uH minimum during the transient, whereas the hard-saturation inductance crashes to near 2uH, or only 10% of its nominal value!

About text formats

Copy of Compare Soft Saturation vs. Regular Inductor - Switching - on Fri, 07/12/2024 - 22:07

Designer0

Member for

4 years 6 months

0

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Description

This design shows the importance of choosing the right inductor size and type, to avoid saturation-induced current spikes during operating transients. In this case, the start-up transient in two nearly identical open-loop buck power stages (12V -&gt; 3V) is examined. The only difference is that the top circuit is using an inductor calibrated to a Coilcraft XAL6060-223 (22uH), which has "soft saturation" behavior. The bottom circuit is using a similarly sized inductor, but with a more typical "hard saturation" characteristic.

Both inductors work well for the steady-state load condition of 3 Amp. But during the turn-on transient, that current can go significantly above that nominal level. At that time, the instantaneous inductance of the hard-saturating device collapses, resulting in even larger current spikes in each switching interval. Note in the waveforms on the left: The soft-saturation inductance drops to 14uH minimum during the transient, whereas the hard-saturation inductance crashes to near 2uH, or only 10% of its nominal value!

About text formats

Copy of Compare Soft Saturation vs. Regular Inductor - Switching - on Fri, 07/12/2024 - 22:07

Designer0

Member for

4 years 6 months

0

designs

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Description

This design shows the importance of choosing the right inductor size and type, to avoid saturation-induced current spikes during operating transients. In this case, the start-up transient in two nearly identical open-loop buck power stages (12V -&gt; 3V) is examined. The only difference is that the top circuit is using an inductor calibrated to a Coilcraft XAL6060-223 (22uH), which has "soft saturation" behavior. The bottom circuit is using a similarly sized inductor, but with a more typical "hard saturation" characteristic.

Both inductors work well for the steady-state load condition of 3 Amp. But during the turn-on transient, that current can go significantly above that nominal level. At that time, the instantaneous inductance of the hard-saturating device collapses, resulting in even larger current spikes in each switching interval. Note in the waveforms on the left: The soft-saturation inductance drops to 14uH minimum during the transient, whereas the hard-saturation inductance crashes to near 2uH, or only 10% of its nominal value!

About text formats

Copy of Compare Soft Saturation vs. Regular Inductor - Switching - on Fri, 07/12/2024 - 22:07

Designer0

Member for

4 years 6 months

0

designs

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Description

This design shows the importance of choosing the right inductor size and type, to avoid saturation-induced current spikes during operating transients. In this case, the start-up transient in two nearly identical open-loop buck power stages (12V -&gt; 3V) is examined. The only difference is that the top circuit is using an inductor calibrated to a Coilcraft XAL6060-223 (22uH), which has "soft saturation" behavior. The bottom circuit is using a similarly sized inductor, but with a more typical "hard saturation" characteristic.

Both inductors work well for the steady-state load condition of 3 Amp. But during the turn-on transient, that current can go significantly above that nominal level. At that time, the instantaneous inductance of the hard-saturating device collapses, resulting in even larger current spikes in each switching interval. Note in the waveforms on the left: The soft-saturation inductance drops to 14uH minimum during the transient, whereas the hard-saturation inductance crashes to near 2uH, or only 10% of its nominal value!

About text formats

Copy of Compare Soft Saturation vs. Regular Inductor - Switching - on Wed, 04/24/2024 - 12:25

Designer0

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4 years 6 months

0

designs

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Description

This design shows the importance of choosing the right inductor size and type, to avoid saturation-induced current spikes during operating transients. In this case, the start-up transient in two nearly identical open-loop buck power stages (12V -&gt; 3V) is examined. The only difference is that the top circuit is using an inductor calibrated to a Coilcraft XAL6060-223 (22uH), which has "soft saturation" behavior. The bottom circuit is using a similarly sized inductor, but with a more typical "hard saturation" characteristic.

Both inductors work well for the steady-state load condition of 3 Amp. But during the turn-on transient, that current can go significantly above that nominal level. At that time, the instantaneous inductance of the hard-saturating device collapses, resulting in even larger current spikes in each switching interval. Note in the waveforms on the left: The soft-saturation inductance drops to 14uH minimum during the transient, whereas the hard-saturation inductance crashes to near 2uH, or only 10% of its nominal value!

About text formats

Copy of Compare Soft Saturation vs. Regular Inductor - Switching - on Sun, 04/21/2024 - 12:20

Designer0

Member for

4 years 6 months

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designs

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Description

This design shows the importance of choosing the right inductor size and type, to avoid saturation-induced current spikes during operating transients. In this case, the start-up transient in two nearly identical open-loop buck power stages (12V -&gt; 3V) is examined. The only difference is that the top circuit is using an inductor calibrated to a Coilcraft XAL6060-223 (22uH), which has "soft saturation" behavior. The bottom circuit is using a similarly sized inductor, but with a more typical "hard saturation" characteristic.

Both inductors work well for the steady-state load condition of 3 Amp. But during the turn-on transient, that current can go significantly above that nominal level. At that time, the instantaneous inductance of the hard-saturating device collapses, resulting in even larger current spikes in each switching interval. Note in the waveforms on the left: The soft-saturation inductance drops to 14uH minimum during the transient, whereas the hard-saturation inductance crashes to near 2uH, or only 10% of its nominal value!

About text formats

Copy of Compare Soft Saturation vs. Regular Inductor - Switching - on Sun, 04/21/2024 - 12:17

Designer0

Member for

4 years 6 months

0

designs

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Description

This design shows the importance of choosing the right inductor size and type, to avoid saturation-induced current spikes during operating transients. In this case, the start-up transient in two nearly identical open-loop buck power stages (12V -&gt; 3V) is examined. The only difference is that the top circuit is using an inductor calibrated to a Coilcraft XAL6060-223 (22uH), which has "soft saturation" behavior. The bottom circuit is using a similarly sized inductor, but with a more typical "hard saturation" characteristic.

Both inductors work well for the steady-state load condition of 3 Amp. But during the turn-on transient, that current can go significantly above that nominal level. At that time, the instantaneous inductance of the hard-saturating device collapses, resulting in even larger current spikes in each switching interval. Note in the waveforms on the left: The soft-saturation inductance drops to 14uH minimum during the transient, whereas the hard-saturation inductance crashes to near 2uH, or only 10% of its nominal value!

About text formats

Copy of Compare Soft Saturation vs. Regular Inductor - Switching - on Tue, 03/19/2024 - 17:11

Designer0

Member for

4 years 6 months

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Description

This design shows the importance of choosing the right inductor size and type, to avoid saturation-induced current spikes during operating transients. In this case, the start-up transient in two nearly identical open-loop buck power stages (12V -&gt; 3V) is examined. The only difference is that the top circuit is using an inductor calibrated to a Coilcraft XAL6060-223 (22uH), which has "soft saturation" behavior. The bottom circuit is using a similarly sized inductor, but with a more typical "hard saturation" characteristic.

Both inductors work well for the steady-state load condition of 3 Amp. But during the turn-on transient, that current can go significantly above that nominal level. At that time, the instantaneous inductance of the hard-saturating device collapses, resulting in even larger current spikes in each switching interval. Note in the waveforms on the left: The soft-saturation inductance drops to 14uH minimum during the transient, whereas the hard-saturation inductance crashes to near 2uH, or only 10% of its nominal value!

About text formats

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Mike Donnelly
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